Method and apparatus for handling yarn



Oct. 20, 1970 N. E. KLEIN METHOD AND APPARATUS FOR HANDLING YARN Filed July 10, 1968 I IINVENTOR. NORMAN E. KLEIN ATTORNEY United States Patent 3,534,452 METHOD AND APPARATUS FOR HANDLING YARN Norman E. Klein, Inman, S.C., assignor to Deering Milliken Research Corporation, Spartanburg, S.C., a corporation of South Carolina Filed July 10, 1968, Ser. No. 753,047 Int. Cl. D02g 1/10 US. Cl. 281.5 8 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for uniformly crimping a running strand of thermoplastic yarn by positively feeding the yarn into a heating zone under relatively low tension to facilitate its contraction during heating, and thereafter pulling the heated yarn strand about a surface of frictional engagement to continuously bend the strand along its length and impose latent stresses therein while controlling the rate of withdrawal of the strand from the surface of engagement to maintain uniform tension in the strand leaving the surface; and apparatus for maintain ing uniform tension in a running yarn strand comprising yarn advancing means, and means for sensing the tension in the portion of the strand passing thereto and for controlling the rate of advancement of the strand by the advancing means to maintain uniform tension in the strand on the input side of the advancing means.

This invention relates to a method and apparatus for handling a moving yarn strand, and more particularly to a method and apparatus for uniformly crimping a thermoplastic yarn, as well as to apparatus for maintaining uniform tension in a running yarn strand during a texturizing or yarn handling operation.

The art of texturizing a thermoplastic yarn to impart elasticity and high bulk properties by an edge crimping process is well known and involves the steps of continuously bending a heated strand of the yarn along its length to impart latent stresses, or crimp, therein and produce an elastic yarn product. The crimped yarn may be subsequently heated to more fully develop these stresses and provide a highly bulked textile yarn product.

Typical apparatus employed in such an edge-crimping operation generally include a yarn heating device for raising the temperature of the yarn above its glass transition point, a crimping member, such as a blade, wire, or rod, for frictionally engaging and bending the heated yarn to impart crimp therein, and suitable yarn guiding and advancing means for continuously withdrawing a strand of the yarn from a supply source, such as a wound bobbin or pirn of yarn, and continuously directing it in a desired yarn path past the heating device and about the crimping member to a collection device.

To facilitate the application of uniform crimp to the strand, it is desirable to maintain the running strand under uniform tension in the area of its engagement with the crimp-imparting member, thus providing for the imposition of more uniform latent stresses in the yarn by its frictional contact with the crimping member. Due to the nature of thermoplastic yarn to contract upon heating, it is also desirable to maintain the yarn strand under relatively low tension during the heating of the yarn prior to its contact with the crimping member to permit it to freely contract without restriction. Various apparatus have been proposed in an attempt to provide these conditions. US. Pat. No. 3,028,654, which is commonly assigned with the present application, discloses an edge-crimping apparatus which employs driven rolls for positively advancing the yarn strand into the heating area at a first rate of linear speed and for positively withdrawing the heated yarn Patented Oct. 20, 1970 ice from the blade crimping member at a slower rate to compensate for average contraction of the yarn during heating. Such positive feeding and withdrawing apparatus does not, however, compensate for the irregular contraction of the yarn during heating which occurs as a result of the non-uniform pressures and stresses imposed on the yarn strand due to the relative position of the strand in the wound yarn supply package. This irregular contraction of the yarn strand during heating subjects the strand to varying tensions at the crimping member and thus reduces the uniform application of stresses and crimp in the yarn by the member.

Another commonly assigned US. Pat. No. 3,017,684, discloses an edge-crimping apparatus wherein tension is controlled in the running yarn on the discharge side of an edge-crimping blade by providing tension sensing means on the discharge side of the blade which operates to variably brake the rotation of a pair of strand-engaging nip rolls located on the input side of the heating Zone preceding the crimping blade, thereby varying the frictional resistance acting on the yarn to adjust the tension in the yarn passing to the blade. This apparatus, however, will maintain uniform tension on the discharge side of the blade only when the tension imposed on the yarn by the braked nip rolls remains greater than any temporary tension rises which may occur in the running yarn strand upstream of the rolls. Any peak tension variations exceeding the tension imposed by the nip rolls will pass along the strand, through the rolls, which amplify the variations, and into the crimping area, resulting in a non-uniform crimping of the yarn. Since the tension imposed on a yarn strand during its withdrawal from a supply package, such as a wound pirn or bobbin, varies considerably in amplitude, depending on the location of the yarn on the surface of the package and the manner in which it is physically removed therefrom, the tension in the yarn heating and edge-crimping areas must always be higher than the peak tension experienced at the yarn supply position if uniform tension is to be maintained. This, of course, requires a relatively high yarn strand tension in the yarn heating area, where it is desirable that the tension be low for proper relaxation and contraction of the strand. It is therefore a primary object of the present invention to provide a method and apparatus for uniformly crimping a running strand of thermoplastic yarn which overcome the disadvantages of the prior art.

It is another object of this invention to provide a method and apparatus for uniformly crimping a running strand of thermoplastic yarn wherein the yarn can be heated under relatively low tension to permit its free contraction, and can be subsequently subjected to a crimping action while under uniform tension conditions to insure the imposition of uniform stress and crimp to the yarn.

It is a further object to provide apparatus for maintaining uniform tension in a running yarn strand during a texturizing or yarn handling operation.

Certain objects of the invention have been stated, other objects will become apparent from the following detailed discussion of the invention and description of the drawings, in which:

FIG. 1 is a schematic perspective view of yarn texturizing apparatus for uniformly crimping a running strand of thermoplastic yarn incorporating the novel features of the present invention; and

FIG. 2 is an enlarged schematic perspective view of the constant tensioning device for maintaining uniform tension in the running strand of yarn on the discharge side of the crimping member of the texturizing apparatus seen in FIG. 1.

Referring more specifically to the drawings, the yarn texturizing apparatus of the present invention generally includes first and second yarn advancing means 10, 12,

positioned in spaced relation for positively advancing a strand of yarn along a desired path of travel, heating means 14 positioned in the yarn path between the advancing means for heating yarn fed thereto, crimping means 16 positioned in the yarn path between the heating means 14 and the second yarn advancing means 12 for frictionally engaging the heated running strand of yarn to continuously bend the strand along its length and impart latent stresses therein, and sensing means 20 positioned in the yarn path between the crimping means and the second yarn advancing means for sensing the tension in the portion of the yarn strand therebetween and for controlling the rate of advancement of the yarn by the second advancing means to maintain uniform tension in the strand leaving the crimping means.

First yarn advancing means comprises a pair of strand-engaging nip rolls 22, 23 which are positively driven to withdraw a yarn strand 21 from a supply source, such as a wound pirn of yarns 24, and continuously positively feed the strand under relatively low tension to heating means 14, which is shown as an electrically heated plate 26, where the temperature of the yarn strand is raised to between its first and second order transition points. The heated yarn strand 21 leaving plate 26 passes into frictional engagement with crimping means 16, which is shown as a sharpedged blade 28, and it is pulled, under higher tension, about the sharp edge of the blade by sec ond yarn advancing means 12 to continuously bend the strand along its length and impose latent stresses therein. The crimped strand is thereafter continuously collected on a free take-up type collection device, such as a ringtraveller take-up spindle 30.

The yarn advancing means 12 and sensing means 20 for maintaining uniform tension in the yarn strand on the discharge side of the crimping blade is best shown in FIG. 2 and comprises a pair of tapered nip rolls 32, 34. Tapered rolls 32, 34, nip rolls 22, 23 and the take-up spindle 30 are drivingly connected by respective pulley and belt arrangements 36, 38, 40 (FIG. 1) to the drive shaft 41 of an electric motor 42. The rotational speeds of these components may be varied, as desired, by changing the size of the drive pulleys. As shown, the right hand tapered roll 32 is positively driven by the pulley and belt arrangement 36 while the left hand roll 34 is supported on a shaft 35 and rotated by frictional engagement with the surface of driven roll 32. The tapered rolls may be constructed of various materials suitable to insure positive advancement of the yarn strand 21 along the yarn path. Preferably, the roll 32 may possess a smooth hard surface, such as stainless steel, aluminum or the like, while the surface of roll 34 may be of a soft material, such as rubber, to insure positive gripping of the strand by the rolls.

Sensing means 20 includes a pivotally mounted guide arm 50 positioned in the yarn path on the input side of the tapered nip rolls 32, 34 for sensing the tension in the portion of the yarn strand passing thereto and for controlling the rate of advancement of the strand by varying the position of the strand path across the surface of the tapered rolls. Arm 50 is pivotally supported along its length on a shaft 52 and has a yarn guide eyelet 53 on one end thereof positioned to guide the yarn strand 21 tangentially onto the distal peripheral surface portion of tapered roll 34, such that the yarn strand passes about an appreciable portion of the surface of roll 34 before entering the nip portion of the rolls to insure positive gripping of the strand by the rolls. As seen in FIG. 2, variation in the position of the strand path along the aXis of the tapered rolls, as shown by the broken yarn path lines P, P", increases or decreases the rate of advancement of the strand along the yarn path.

Attached to the other end of guide arm 50 by a spring 54 is a weight 56 which provides a constant torque to bias the arm 50 in a clockwise direction of pivotal movement about shaft 52, as seen in FIG. 2. The spring 54 serves as a compliant member to isolate the mass of the weight 56 and avoid sudden displacement of the weight during pivotal displacement of the yarn. Although the means for biasing the pivotal arm is shown as a weighted member, other means may be readily employed to provide a substantially constant torque in the arm, such as a constant torque motor or other elastic member having a relatively low spring constant and operating over a relatively small deformation range. To prevent over control or over shoot once corrective action has been sensed and movement initiated in arm 50, damping means, such as a pneumatic piston-type damping pot 58 may be provided and attached to the arm to control the rate of movement of the same.

In operation, the strand of thermoplastic yarn 21 is axially withdrawn from the wound yarn pirn 24 and positively fed by nip rolls 22, 23 across the surface of the heating plate 26 where the yarn is under relative low tension and free to contract during heating. By positively feeding the strand into the heating zone by the use of the driven nip rolls, irregular tension variations occurring in the running strand upstream of the rolls, particularly during removal of the strand from the yarn package, are isolated from the heating zone, thereby preventing sudden undesirable rises in tension in the yarn in the heating area and at the crimping blade. Heated yarn leaving the heating plate is pulled by the driven tapered rolls 32, 34 about the edge of the crimping blade 28 to continuously bend the strand along its length and impose latent stresses therein. The portion of the yarn strand leaving the crimping blade passes upwardly, through the guide eyelet 53 of the pivotal arm, and about the surface of the tapered nip rolls 32, 34. At times when strand tension on the discharge side of the blade temporarily increases, the guide arm 50 pivots in a counterclockwise direction against the biasing force of weight 56 to displace the path of the yarn on the surface of the tapered rolls toward the smaller diameter end of the rolls, thereby reducing its rate of with drawal from the blade and lowering the yarn tension to the desired preselected tension level. In like manner, a temporary decrease in the tension level in the strand on the discharge side of the blade causes the guide arm to pivot in a clockwise direction, displacing the yarn path toward the larger diameter end of the tapered rolls to increase its rate of withdrawal and maintain the preselected tension level.

To provide optimum sensitivity of the guide arm 50 to these slight variations in tension in the yarn strand, it is desirable that the path of the strand between the blade 28 and the guide eyelet 53 be substantially perpendicular to the arm and its pivotal axis, while the portion of the strand passing from the eyelet 53 to the surface of the tapered roll 34 is preferably maintained generally parallel to the pivotal axis of the guide arm 50 to provide optimum track of the strand over the surface of the rolls.

Although the crimping apparatus of the present invention has been described as employing a heating plate and a blade member to respectively heat and crimp the run ning yarn, other means may be so employed without departing from the scope of the invention. For example, the heating member may be a heated roll or tube, while the means providing a surface of frictional engagement to crimp the running yarn may be a rod, wire, air jet, or a portion of the running yarn strand itself. Also, the tension in the yarn at the discharge side of the blade might be sensed and controlled by other means, such as an electromechanical or fluidic-mechanical transducer in combina tion with a variable speed motor connected to withdrawal rolls or capstans.

Thus it can be seen that by providing at all times a uniform tension on the discharge side of the crimping blade, substantially uniform stresses can be imparted to the strand to provide a uniformly crimped yarn. By additionally providing means for positively feeding the yarn into the heating zone to maintain the yarn under relatively low tension therein, the yarn is free to contract,

thus further facilitating the application of uniform crimp therein.

The foregoing drawings and specification have set forth preferred embodiments of the invention and, although specific terms have been employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

That which is claimed is:

1. A method of uniformly crimping a running strand of thermoplastic yarn comprising the steps of:

(a) continuously withdrawing the yarn strand from a yarn supply source,

(b) positively feeding the strand into a heating zone to isolate the tensions imposed on the strand during its withdrawal from the supply source and to maintain the strand under relatively low tension in the heating zone to facilitate its contraction during heating,

(c) heating the strand in said zone to between its first and second order transition points, and

(d) pulling the heated strand about a surface of fricthereof to maintain a uniform tension in the strand along its length and impose latent stresses therein, while controlling the rate of withdrawal of the strand from the surface of engagement on the outflow side thereof to maintain a uniform tension in the strand leaving the surface.

2. A method as defined in claim 1 wherein the rate of withdrawal of the yarn strand is controlled by sensing the tension in the portion of the yarn strand leaving the surface of engagement, and by varying the rate of withdrawal of the strand in response to variations in the tension therein.

3 Apparatus for uniformly crimping a running strand of yarn comprising (a) first and second yarn advancing means positioned in spaced relation for positively advancing a strand of yarn along a desired path of travel,

(b) heating means positioned in the yarn path between said first and second yarn advancing means for heating yarn fed thereto by said first yarn advancing means,

(c) means positioned in the yarn path between said heating means and said second yarn advancing means for frictionally engaging the heated running strand to continuously bend the strand along its length and impart latent stresses therein, and

(d) means positioned in the yarn path between said yarn strand engaging means and said second yarn advancing means for sensing the tension in the portion of the yarn strand therebetween and for controlling the rate of advancement of the strand by said second yarn advancing means to maintain uniform tension in the strand leaving the strand engaging means, thereby facilitating application of uniform stresses in the running strand.

4. Apparatus as defined in claim 3 wherein said yarn strand engaging means comprises a blade member having a relatively sharp, strand-engaging edge positioned to define an abrupt bend in the yarn path; said second yarn advancing means comprises a pair of driven tapered nip rolls for engaging the yarn strand over a portion of their peripheral surfaces and for pulling the strand about the blade edge; and said tension sensing and controlling means includes yarn guide means positioned adjacent the input side of the tapered nip rolls and being dispaceable in response to variations in tension in the portion of the yarn strand passing from the blade edge to the tapered rolls to correspondingly vary the position of the path of the yarn strand across the surface of the tapered rolls to increase or decrease the rate of advancement of the strand.

5. Apparatus as defined in claim 3 wherein said second yarn advancing means includes a conical strand engaging drive surface, and said sensing and control means comprise an elongate member pivotally mounted along its length and having strand engaging means adjacent one end thereof positioned adjacent said conical drive surface, and means biasing said member in a first pivotal direction to support and direct the strand into contact with the conical drive surface whereby variations in tension in the running strand cause pivotal movement of said elongate member to vary the position of the strand across said drive surface and thereby increase or decrease its rate of advancement thereby.

6. Apparatus as defined in claim 5 wherein said biasing means comprises a weight attached to said elongate member on a side opposite the pivot point thereof from said strand engaging means.

7. Apparatus as defined in claim 6 including spring means connecting said weight to said elongate member, and damping means connected to said elongate member to control the rate of pivotal movement of said member.

8. Apparatus for maintaining uniform tension in a running strand of yarn comprising yarn advancing means including a conical strand engaging drive surface for positively advancing a strand of yarn along a desired path of travel, an elongate pivotally mounted arm having a yarn guide displaced from the pivot point thereof and positioned in the yarn path on the input side of said drive surface for directing the running strand into contact with said drive surface, and a weight attached to said pivotally mounted arm on the opposite side of the pivot point thereof from said yarn guide for biasing said arm in a first direction of pivotal movement to support the running strand such that varying tension on the strand passing into contact with said conical drive surface displaces the arm to correspondingly vary the position of the path of the strand across said drive surface and thereby increase or decrease its rate of advancement thereby.

References Cited UNITED STATES PATENTS 2,758,358 8/1956 Shattuck 28-1.7 2,985,393 5/1961 Zander 242-18 3,017,684 1/1962 Pittman 2872.13

LOUIS K. RIMRODT, Primary Examiner US. Cl. X.R. 2872.13; 242-18 CERTIFICATE OF CORRECTION Patent No. 3 5'34 45Z Dated October 20, 1970 Inventofls) Norman E. Klein It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 19, change "yarns" to --yarn--.

Column 5, Claim 1, rewrite "(d)" as follows: -(d) pulling the heated strand about a surface of frictional engagement to continuously bend the strand along its length and impose latent stresses therein, while controlling the rate of withdrawal of the strand from the surface of engagement on the outflow side thereof to maintain a uniform tension in the strand leaving the surface.

Column 6, line 5, change "dispaceable" to --displaceable--.

Mill 1 9 1Q?! Attestinz Officer mm B. SGHUYLHR, J12 sinner of Patents 

